The invention relates to a system comprising a compressor, a control unit and a clutch which is assigned to the compressor, with the control unit being suitable for opening and closing the clutch in order to save energy.
The invention also relates to a method for controlling a system comprising a compressor, a control unit and a clutch which is assigned to the compressor, with the control unit opening and closing the clutch in order to save energy.
Modern commercial vehicles usually have a compressed air supply system which provides cleaned and dried compressed air for various systems of the commercial vehicle. For example, the service brakes and a possibly provided air suspension system of the commercial vehicle are supplied by the compressed air treatment system. The compressed air treatment system may have integrated within it a control unit for actuating the electric solenoid valves and for evaluating sensor signals. The solenoid valves may alternatively also be actuated according to various system parameters by an external control unit. Such control units receive further system parameters via a serial communication connection, for example the CAN bus. It is for example possible for data of the service brake and a possibly provided air suspension system to be transmitted to the compressed air treatment system. The compressed air treatment system itself receives the still non-cleaned and non-dried compressed air from a connected compressor. The energy for operating the compressor may be transmitted in a simple manner from the drive engine of the commercial vehicle to the compressor via a shaft.
Since the demand for compressed air within the commercial vehicle normally does not require continuous operation of the compressor, a clutch may be provided between the drive engine and the compressor in order to enable decoupling between the compressor and drive engine. This is desirable because the operation of the compressor consumes energy which can be saved if no compressed air is required, or if the present compressed air reserve can cover the compressed air demand of the consumers for a period of time. The idle phases during which energy can be saved in the decoupled state of the compressor are very long in particular in highway driving situations, since then the compressed air consumption, in particular by the service brake, is low.
In addition to the simple functionality for saving energy, the clutch may however also cause defects during the operation of the compressor and of the components connected downstream of the compressor, or the clutch itself may fail as a result of a defect.
The invention is based on the object of providing a compressor system which can detect defects of the system and automatically prevent at least some impending defects of the system.
This and other objects are achieved by a system and method of operating same, comprising a compressor, a control unit and a clutch which is assigned to the compressor, with the control unit being suitable for opening and closing the clutch in order to save energy. The control unit is suitable for carrying out a monitoring routine during the course of which the clutch is opened or closed in order to prevent damage to the clutch, the compressor and components situated downstream of the compressor.
The method is advantageously refined in that a slip of the closed clutch is monitored during the course of the monitoring routine. By monitoring the slip of the closed clutch, it is possible to detect increasing wear of the clutch or a defective closure of the clutch.
It may expediently be provided that an opening of the clutch is monitored during the course of the monitoring routine. By monitoring the opening of the clutch, it is possible to detect a defective switching, in particular an incomplete opening, of the clutch.
Furthermore, the monitoring routine may provide a minimum time period between two clutch actuations. Multiple actuations of the clutch within short periods of time result in intense wear on account of the disproportionate heating, and this leads to premature failure of the clutch. The provision of a minimum time period between two clutch actuations therefore increases the overall service life of the clutch.
It is also possible for the monitoring routine to provide a maximum time period during which the clutch is open. In the open state, the compressor situated downstream of the clutch is not in operation. The compressor is usually lubricated by means of oil which, during operation, is delivered continuously from an oil sump into the region between a piston and a cylinder wall. As a result of the opening of the clutch, the oil delivery is also stopped, wherein after a certain amount of time there will no longer be sufficient lubrication between the piston and the cylinder wall, since the oil which was originally present there has flowed back into the oil sump. Therefore, in the event of a re-start of the compressor as a result of a closure of the clutch, the result is increased abrasion to the piston and cylinder wall. This can be prevented by means of a maximum time period during which the clutch is open, because sufficient lubrication between the piston and cylinder wall can be ensured by means of re-delivery of oil.
It may be provided here in particular that the maximum time period during which the clutch is open is dependent on an ambient temperature. If the ambient temperature of the compressor is such that a delivery line situated downstream of the compressor can freeze, then it is possible in this way, in the event of the risk of frost, for the delivery line to firstly be deaerated and then blown dry such that condensation water is expelled. By means of cyclic activation of the compressor, it is possible for the delivery line to be consistently held at temperature with warm air.
It may expediently be provided that the compressor rotational speed is monitored during the course of the monitoring routine. If the determined compressor rotational speed is greater than a permitted maximum compressor rotational speed, then the compressor can be protected from mechanical damage by virtue of the clutch being opened.
It may also be provided that the clutch rotational speed is monitored during the course of the monitoring routine. The clutch may also be protected from mechanical overloading by monitoring the rotational speed, wherein the clutch is opened if the clutch rotational speed is too high.
It may expediently also be provided that, during the course of the monitoring routine, data are stored in order to permit a fault diagnosis or statistical evaluation. The storage of data makes a subsequent extended fault diagnosis possible, by which research can be carried out into the cause of the fault which has occurred, thereby permitting a further improvement in the system.
It may preferably be provided that, during the course of the monitoring routine, a warning signal is output if a component of the system is operating defectively. If the monitoring routine detects an irregularity with regard to the clutch or another part of the system, then as a result of the output of a warning signal, in the form of a warning lamp, an acoustic signal or a communication via a display of an on-board instrument, the vehicle driver can be informed and can initiate corresponding counter measures, in particular can seek a service station before a complete failure which would possibly prevent onward travel of the vehicle. Ideally, the clutch function is then deactivated in order to prevent further damage.
The invention also relates to a commercial vehicle having a system according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.